Anomalous Contact Angle Hysteresis of a Captive Bubble: Advancing Contact Line Pinning

Abstract

Contact angle hysteresis of a sessile drop on a substrate consists of continuous invasion of liquid phase with the advancing angle (θ(a)) and contact line pinning of liquid phase retreat until the receding angle (θ(r)) is reached. Receding pinning is generally attributed to localized defects that are more wettable than the rest of the surface. However, the defect model cannot explain advancing pinning of liquid phase invasion driven by a deflating bubble and continuous retreat of liquid phase driven by the inflating bubble. A simple thermodynamic model based on adhesion hysteresis is proposed to explain anomalous contact angle hysteresis of a captive bubble quantitatively. The adhesion model involves two solid–liquid interfacial tensions (γ(sl) > γ(sl)′). Young’s equation with γ(sl) gives the advancing angle θ(a) while that with γ(sl)′ due to surface rearrangement yields the receding angle θ(r). Our analytical analysis indicates that contact line pinning represents frustration in surface free energy, and the equilibrium shape corresponds to a nondifferential minimum instead of a local minimum. On the basis of our thermodynamic model, Surface Evolver simulations are performed to reproduce both advancing and receding behavior associated with a captive bubble on the acrylic glass.

Dissolution of a spherical cap bubble adhered to a flat surface in air-saturated water

“…As previously discussed in § 2.1, the (quasi-static) contact angle dynamics along a smooth homogeneous surface may be suitably characterized by the adhesion hysteresis model proposed by Hong et al (2011). Upon bubble inflation, the model predicts the contact angle to remain constant at the initial receding angle θ r .…”

“…equilibrium angle, and that it completely describes the contact line dynamics (Snoeijer & Andreotti 2013). Hong et al (2011) recently proposed a thermodynamic model based on adhesion hysteresis able to predict the static CAH for SCBs enduring sequential changes in volume. The physical explanation for the observed CAH is that the separation energy required to make the liquid phase recede (bubble inflation characterized by an increasing SCB contact radius) is greater than the adhesion energy given by an advancing liquid phase (bubble deflation c haracterized b y a d ecreasing SCB contact radius).…”

Facile manipulation of receding contact angles of a substrate by roughening and fluorination

“…In the process of inflation and deflation of a sessile drop on a real surface, a hysteresis loop can be evidently observed in the plot of CA versus drop volume. This phenomenon is so-called contact angle hysteresis (CAH), which is described by the difference between the advancing and receding CA ( Â = Â a − Â r ) [7][8][9]. CAH generally appears through the pinning-depinning behavior of the contact line.…”

“…a simple modification of the above method and  r is acquired as the evaporating drop begins to shrink [10][11][12][13][14][15][16][17]. In general, CAH on a real surface is attributed to two mechanisms: (i) adhesion hysteresis associated with molecular rearrangement on solid surfaces by wetting [7,18,19], (ii) localized defects associated with hydrophilic blemishes or surface roughness [20][21][22][23]. In the first mechanism, the restructuring of the solid surface in contact with liquid results in the reduction of solid-liquid interfacial tension, which is corresponding to the receding CA.…”

Influence of surface treatment on PEDOT coatings: surface and electrochemical corrosion aspects of newly developed Ti alloy

“…In general, contact angle hysteresis (CAH ¼ cos q adv À cos q rec ) is the difference between the advancing and receding contact angles. The importance of CAH has been effectively studied by several researchers, 40,41 and the common conclusion is that it mainly arises from the chemical and topographical heterogeneity, surface deformation, and adsorption and desorption, swelling and penetration. 42 Dynamic contact angle images of untreated and treated TNZ surface were measured and the images were presented as ESI in Fig.…”